A coalition of NYPD cops hired an aerial-advertising company to send a pointed message to Mayor de Blasio high over the Hudson River.

“De Blasio, Our Backs Have Turned to You,” read a banner a small plane towed up and down the Hudson at about 9 a.m.

Former and current cops coughed up about $1,000 to hire Ashley Chalmers, owner of Jersey Shore Aerial Advertising, who flew their missive to the mayor around the city for nearly three hours.

They also sought help from blogger and former NYPD cop John Cardillo, who was contacted by a retired detective and ­active-duty supervisor on Christmas Eve.

The pair asked him to publish a statement they had written as soon as their diss at de Blasio started soaring through the sky — adding that more than 200 cops backed their high-flying plan.

“As a large and unified group of current and retired NYC Police Officers, Detectives & Supervisors, we are outraged by the mayor’s incendiary rhetoric, and for facilitating the current hostile climate towards the NYPD,” began the statement, which was posted at 8:50 a.m..

The officers fumed that de Blasio shows them “no respect” — and has ­encouraged New Yorkers to do the same.

“It is our opinion that Mayor de Blasio’s dangerous and irresponsible comments about his and his wife’s concern for their son’s safety at the hands of the NYPD fueled the flames that led to civil unrest, and potentially to the deaths of PO Wenjian Liu and PO Rafael Ramos, as well as the continued threats against NYPD personnel,” the statement said.

They ultimately renounce Hizzoner, saying they no longer have confidence in his ability to lead the city.

“Mayor de Blasio turned his back on us long before we turned our backs on him,” the statement concludes.

Chalmers took off from Jersey Regional Airport at about 8:45 a.m., then flew over the Verrazano Bridge before heading north toward the George Washington Bridge, where he turned back around. The pilot looped around the river four or five times, he said.

The cops chose the Hudson River out of respect for Ramos’ family, who held a well-attended wake for the slain cop in a Queens church Friday afternoon.

“Dividing people won’t help our city heal,” City Hall spokesman Wiley ­Norvell said in reaction to the banner.

Meanwhile, the head of a union representing New York City police traffic-enforcement agents said his members should get bullet-proof vests, police escorts and perhaps some jujitsu training because the recent surge of cop haters don’t distinguish between them and real cops who carry guns.

“We’re sitting ducks,” CWA Local 1182 president Robert Cassar told The Post. “If someone fires at one of us, all we can do is run and hope the bullet doesn’t catch us.”